When I try to press R (for <RETURN>), PC gives a 'bip' and don't do nothing
what the hell made you think it was 'R' ? 'return' is the 'enter' key.
boot splash screens use framebuffer, usually via vesafb(-tng), and vesa modes don't include modes outside the ultra-standard ones (like 640x480, 800x600, 1024x768). some vesa vbe tools I can't recall will give you the vesa mode list your card can support.